Question

How many protons z and how many neutrons n are there in a nucleus of the most common isotope of silicon, 2814si?

Answer 1

The 28 is the sum of the protons and neutrons in the element silicon.
ALL silicon atoms have 14 protons in the nucleus, so we can turn this into an equation:
#protons + #neutrons = 28
14 + #neutrons = 28
#neutrons = 14
#protons = 14

Answer 2

Answer: 14 protons and  14 neutrons

Explanation:

Atomic number is defined as the number of protons or number of electrons that are present in an atom.

Atomic number = Number of electrons = Number of protons = 14

Mass number is defined as the sum of number of protons and neutrons that are present in an atom.

Mass number = Number of protons + Number of neutrons = 28

Number of protons + Number of neutrons = 28

14 + Number of neutrons = 28

Number of neutrons = 14

Thus there are 14 protons and  14 neutrons in $^{28}_{14}\textrm {Si}$